Temporal lobe epilepsy is perhaps the most common form of partial seizures. Although medical treatment controls seizures in the majority of patients, as many as 20% of cases remain refractory to medical intervention and are referred eventually for possible surgical treatment. Accurate localization of the epileptic focus is necessary before surgery is contemplated. This has largely and traditionally been depending on scalp and invasive electroencephalographic (EEG) investigations. However, recent technological developments have greatly assisted in the investigation and selection of these patients. Magnetic resonance imaging (MRI) and Positron Emission Tomography (PET) provide important independent information about the epileptic focus. MRI can reliably detect foreign tissue lesions and mesial temporal sclerosis in the majority of temporal lobe epilepsy patients investigated for surgery. Additionally, PET may demonstrate interictal hypometabolism in the affected epileptogenic tissue. Magnetic Resonance Spectroscopy (MRS) can contribute to our understanding of particular details of in vivo cell metabolism and intrinsic cell energetics not amenable to other methods. In vivo 31P MRS provides the levels of high energy phosphate metabolites and derivative molecules of phospholipid metabolism. To further explore our present knowledge of the functional metabolic disturbances demonstrated by PET studies in temporal lobe epilepsy, we wish to investigate the use of 31P MRS in patients with intractable temporal lobe seizures as well as in patients with secondary generalized epilepsies. We hypothesize that certain metabolic changes detected by MRS will add independent and confirmatory evidence for seizure localization in patients with temporal lobe epilepsy, thus allowing noninvasive diagnosis. Localized 1H MRS will provide levels of GABA, glutamate and lactate in both groups of patients. In preliminary studies at 2T we found that in vivo measurements of brain phosphate metabolites by 31P MRS in a small group of selected patients with medically intractable temporal lobe epilepsy revealed a significant reduction in the temporal lobe responsible for seizure generation of the level of phosphocreatine, a central compound in high energy phosphate metabolism. Patients with temporal lobe epilepsy had marked depressions of the PCr/Pi ratio in the ipsilateral temporal lobe compared to the contralateral lobe and when compared to non-epileptic subjects. In addition, a mild depression of PCr/Pi was found int he contralateral temporal lobe when compared to controls. The proposed study will be carried out to allow statistically significant conclusions. Also, with the availability of our 4.1T MR instrument providing improved sensitivity and resolution previously contradictory results on intracellular pH in epileptic brains, obtained by different research groups, will be elucidated.